Interior Secretary Ken Salazar announced that he would be leaving the Cabinet in March and will return to Colorado.

WASHINGTON — Ken Salazar, the blunt-spoken lawyer and rancher who took over the scandal-ridden Interior Department at the outset of the Obama administration, said Wednesday that he would step down in March to return to his home in Colorado.

He did not say what he intended to do after leaving Washington, and the White House gave no hint of who might succeed him.

Salazar’s exit, along with the announced resignation of Lisa P. Jackson, the administrator of the Environmental Protection Agency, and the anticipated departure of Energy Secretary Steven Chu, will leave vacant the critical Cabinet posts dealing with climate change and energy, among the most pressing challenges facing the nation.

President Barack Obama, who entered the Senate with Salazar in 2005, said that the interior secretary had helped expand the development of domestic energy resources while also protecting land, water and wildlife.

“In his work to promote renewable energy projects on our public land and increase the development of oil and gas production,” the president said in a statement, “Ken has ensured that the department’s decisions are driven by the best science and promote the highest safety standards.”

In his four years in office, Salazar, 57, has taken steps to turn the Interior Department from its historic focus on mining, forestry and oil and gas development on public lands to a new emphasis on the development of renewable energy. Since 2009, the department has authorized 34 large solar, wind and geothermal energy projects, which eventually will produce more than 10,000 megawatts of electricity, enough to power more than 3 million homes.

Salazar also oversaw the settlement of a 15-year legal battle waged by American Indian tribes claiming that the federal government had cheated them out of billions of dollars in trust assets and lands managed by the Interior Department. The so-called Cobell suit was filed during the Clinton administration and resolved in 2009 with a $3.4 billion settlement that brought cash and land to thousands of tribal members and organizations.

He also established seven new national parks and 10 new national wildlife refuges, and he blocked uranium mining in a 1 million-acre buffer zone around the Grand Canyon.

But his tenure will be most remembered for his handling of contentious oil and gas issues, like the BP Deepwater Horizon oil spill and the decision to allow Shell to explore for oil in the Alaskan Arctic.

The BP disaster, in April 2010, killed 11 workers, fouled the Gulf of Mexico with millions of barrels of oil, and laid bare incompetence and corruption at the Minerals Management Service, the Interior Department agency responsible for regulating oil and gas operations on public lands and waters.

Obama chided the interior secretary for using cowboy language — Salazar said of BP officials, “We have our boot on their neck to make sure they get the job done” — and for having moved too slowly to reform the minerals service despite years of obvious mismanagement and even criminal behavior.

At the White House’s urging, Salazar brought in Michael R. Bromwich, a tough former top Justice Department official, to dismantle the regulatory agency and rebuild it as three separate agencies with clear authority over leasing, revenue collection, and safety and environmental protection.

The new agencies adopted rigorous rules for well safety and spill response, and they cleaned up a leasing process that under previous administrations had deprived the federal government of billions of dollars in oil and gas royalty payments.

Salazar, a fifth-generation Mexican-American who favors Western hats and bolo ties, had served as Colorado’s attorney general and the head of its Department of Natural Resources before his election to the Senate in 2004. His brother, John Salazar, represented Colorado in the House from 2005 to 2011.

As he juggled repeated crises in Washington, Salazar often spoke longingly of his life on the family ranch near the New Mexico border. He and his wife, Esperanza, are the primary caregivers for an autistic 5-year-old granddaughter.

“Colorado is and will always be my home,” Salazar said in the statement announcing his departure.